Power supplies for portable electrical devices

Abstract: A portable computer main body (10) includes a power source circuit section (46) having a battery pack. A plurality of auxiliary battery units (16-1, 16-2) are mechanically connected and fixed to a casing of the computer main body and are electrically connected in series to a power source input terminal (48) of the main body (10). A charge/discharge control section (52-1, 52-2) is provided for each of the auxiliary battery units (16-1, 16-2). During charging, the charge/discharge control sections cooperate to charge the auxiliary battery units sequentially starting from the auxiliary battery unit (16-1) located nearest to the computer main body (10). On the contrary, during discharging (use of the computer) the charge/discharge control sections cooperate to discharge the auxiliary battery units sequentially starting from the auxiliary battery unit (16-2) which is furthest from the computer main body. There is also another system construction having a single auxiliary battery.

Description: The invention relates to power supplies for portable electrical devices, for example personal computers which are driven by battery power sources. Since the use, and in particular outdoor use, of portable personal computers of the notebook type is increasing, it is required that such computers can be used for a long time even in a state in which.there is no AC adapter or the like. Conventionally, as a battery unit of a portable type personal computer, a combination of a main battery unit built into the personal computer main body and an auxiliary battery unit is used. The auxiliary battery unit, which is attachable to the outside of the personal computer, is a unit simply having a battery therein and enables the total battery capacity of the computer to be increased. In case of charging the auxiliary battery unit, the auxiliary battery unit is detached from the computer main body when completely exhausted, and is connected to an AC adapter, used to charge the exhausted battery unit exclusively, and is charged. Therefore, when an auxiliary battery unit is used, in a state where there is no AC adapter, there is a problem in that operations requiring a capacity larger than the combined capacity of the battery unit built into the personal computer main body and one auxiliary battery unit cannot be performed. Also, it is difficult to achieve operation of the computer for a satisfactorily long period. Even if a plurality of auxiliary battery units are prepared, it is still troublesome to exchange the batteries during operation of the computer. When charging, it is necessary to charge each auxiliary battery unit. When a plurality of units are to be charged, there is a problem that the exchange of the batteries for charging must be done many times. Further, when a freshly-charged battery unit is connected, after the battery unit built into the computer main body has been completely exhausted, the computer is switched to receive power from the auxiliary battery unit attached to the outside. Due to this, even when the auxiliary battery unit becomes exhausted some time later, the power supply to the computer is completely stopped. Therefore, even if a plurality of auxiliary (spare) battery units are prepared, it is impossible to continuously use the computer while exchanging the spare battery units, and so there is a problem in that the use of the computer must be temporarily stopped each time the auxiliary battery unit is changed. EP-A-0463593 may be considered to disclose apparatus comprising a portable electrical device and respective first and second battery units, each battery unit including one or more rechargeable batteries, for supplying electrical power to circuitry of the device; each of the battery units having an input for receiving electrical power for charging its said one or more batteries and an output for delivering electrical power from its said one or more batteries; and the battery units being connected and controlled, when the apparatus is in use, such that when an external power supply source is connected to the apparatus the first battery unit is charged first and then the second battery unit is charged, and such that when no such external power supply source is connected the said circuitry is powered first by the said second battery unit, until that unit is discharged, and then by the said first battery unit. In this apparatus, both the first and second battery units are connected in parallel with one another within the portable electrical device, the second battery unit being semi-fixed by a screw whilst the first battery unit is slidably detachable. A dedicated power control CPU, belonging to the portable electrical device and provided in common to both battery units, selects which battery unit is to be charged or used to power the device at any given time. Apparatus embodying the present invention is characterised in that, during such sequential charging and such sequential powering, the first and second battery units are connected together in a series configuration in which the input of the first battery unit is connected to the output of the second battery unit, the said circuitry being connected on the output side of the first battery unit; and in that each of the battery units has control means which co-operate to bring about the said sequential charging when such an external power supply source is connected to the apparatus, and to bring about the said sequential powering when no such external power supply source is connected. One embodiment of the invention, applied to a portable computer, comprises: a portable computer main body having therein a power source circuit section; and a plurality of auxiliary battery units (the first and second battery units) which are connected and fixed mechanically to a casing of the computer main body and is also electrically serially connected to a power source input terminal of each unit. In the above power source system a battery circuit section is provided for each auxiliary battery unit. At the time of charging the battery circuit sections cooperate so as to sequentially complete the charging starting from the auxiliary battery unit which is located on the computer main body side. On the other hand, at the time of discharging (i.e. when powering the portable computer) the battery circuit sections cooperate so as to sequentially supply a power source starting from the auxiliary battery unit which is farthest from the computer main body. In such a power source system one of the auxiliary (spare) battery units can be exchanged and charged whilst the computer remains in use and, further, the apparatus can be continuously used for a long time and can have a power source capacity which is proportional to the number of spare battery units. Embodiments of the invention are applicable to the power source systems of any electrical device which can be powered using a battery. Preferably, the battery circuit section of the spare battery unit has a battery pack therein and has an input terminal and an output terminal. An output terminal of the other auxiliary battery unit or an output terminal of the AC adapter for converting an AC power source to a DC power source and generating is connected to the input terminal. The output terminal is connected to an input terminal of the other auxiliary battery unit or an input terminal of the power source of the computer main body. An input power source voltage from the input terminal is detected by a voltage detecting section. The connection of an AC adapter or the connection of the other holding battery unit can be discriminated by the detected voltage. An output current to the output terminal is detected by a current detecting section. A first discharging switch to turn on or off the power source supply is provided for a power source line to the output terminal. A second discharging switch to turn on or off the power source supply is provided for an output line from a battery pack. Further, a charging switch to turn on or off the power source supply is provided for a charging line from the input terminal to the spare battery power source. A charge control section which is realized by a microprocessor detects the connection of the AC adapter from the detected voltage of the input terminal and only when the detected current to the output terminal is equal to or less than a predetermined value, the charging switch is turned on, thereby charging to the battery pack. In the case where the connection of the AC adapter or another auxiliary battery unit is detected from the detected voltage of the input terminal, in one embodiment of the invention a discharge control section which is realized by a microcomputer turns on the first discharging switch and also turns off the second discharging switch and supplies an external power source to the front stage unit. In the case where no connection of the AC adapter or another auxiliary battery unit is detected from the detected voltage of the input terminal, the discharge control section both of the first and second discharging switches are turned on and a power source is supplied to the front stage from the self battery pack. Preferably, the charging switch includes a high speed charging section to a supply a current which is close to the maximum allowable charging current of the battery pack and to thereby charge at a high speed, and a trickle charging section to supply an arbitrary current which is determined by a potential difference between the input power source voltage and the charge voltage of the battery pack and a specified resistance and to charge and connected in parallel to the charge switching section. When the detected current to the output terminal is equal to or less than a predetermined value in a state in which the connection of the AC adapter is detected, the charge control section makes the high speed charging section operative, thereby charging at a high speed. When the detected current to the output terminal exceeds the predetermined value, the trickle charging section is made operative, thereby trickle charging. In this embodiment, when any one of the following three conditions is obtained, the charge control section turns off the charge switch section, thereby stopping the charging: I. when the elapsed time of a timer which is activated at the start of the charging reaches a predetermined time; II. when the detected temperature by a temperature sensor provided for the spare battery power source exceeds a predetermined temperature; III. the power source voltage of the spare battery power supply is observed, and when a change such that the voltage which is rising in association with the charging exceeds the peak voltage and decreases is detected. Further, a display section to show a state of the spare battery unit and/or system may be provided for the spare battery unit. Advantageously, the display section displays at least an input state of the external power source voltage for the input terminal, a charging state, and a state of the battery voltage. The display section may display information only during the ON operation of the display switch. The discharge control section detects a discharged current of the battery pack and turns off the second discharging switch and detaches the battery pack when the current becomes excessive. Alternatively, or in addition, when the discharged voltage of the battery pack is detected and is equal to or less than a specified voltage, the discharge control section turns off both of the first and second switches and shuts off the power source supply to the unit at the front stage. In one embodiment the power source circuit section provided for the computer main body is substantially the same as the built-in circuit of the spare battery unit except that the first discharging switch is not provided. Therefore, a plurality of auxiliary battery units can be connected and used and the computer can be driven for a long time according to the number of auxiliary battery units connected. When charging, it is also possible to sequentially charge from the unit on the computer side in a state in which a plurality of auxiliary battery units are connected, and it is possible to easily charge without detaching each unit. Further, when the computer is used, the discharging is sequentially executed starting from the spare battery unit which is located on the outside (i.e. farthest from the computer). Therefore, in case of detaching some of the auxiliary battery units, it is possible to easily detach one auxiliary battery unit from another auxiliary battery unit which has become exhausted. Further, when the computer is in use, and the AC adapter is connected, if there are some units with exhausted battery packs, they can be charged sequentially starting from the unit on the computer main body side. In this case, if the computer is in a stand-by state in which current consumption is small, a high speed charging is executed. When the computer is in an operation state in which a current consumption is large, a trickle charging is executed. Another embodiment of the invention has a construction such that a single spare battery unit (the second battery unit) is connected to the computer main body, the first battery unit being contained within the computer main body. In this case, in the spare battery unit it is possible to omit the second discharging switch provided for the output line of the spare battery power source (this switch is provided in the above described embodiment having a plurality of spare battery units), the remaining circuitry of the spare battery unit being substantially the same. The power source circuit section of the computer main body in this case may be the same as the above-described power source system to which a plurality of spare battery units can be connected. In the power source system to which the single spare battery unit is connected, it is possible to charge while the auxiliary battery unit is connected and there is no need to detach the auxiliary battery unit, so that it is possible to easily charge. When the computer is used, the discharging is started from the spare battery unit and when the spare battery unit is fully finished, the discharging mode is switched to the discharge from the battery pack of the main body. Further, by connecting the AC adapter when the computer is used, if there are some units with fully exhausted battery packs, the charging can be sequentially executed while using the computer in accordance with the order of the battery pack built in the computer main body and the spare battery unit. Reference will now be made, by way of example, to the accompanying drawings, in which: Fig. 1 is an explanatory diagram showing an embodiment of a first aspect of the invention in which a plurality of auxiliary battery units are connected to a computer; Fig. 2 is an exploded diagram corresponding to Fig. 1; Fig. 3 is a rear view of one of the auxiliary battery units; Fig. 4 is a plan view of the auxiliary battery unit; Fig. 5 is a front view of the auxiliary battery unit; Fig. 6 is a left side view of the auxiliary battery unit; Fig. 7 is a block diagram showing a power source system embodying the invention; Fig. 8 is a block circuit diagram showing one example of the construction of a battery circuit section of a spare battery unit of the Fig. 7 system; Fig. 9 is a flowchart showing a processing operation of the Fig. 8 battery circuit section; Fig. 10 is a flowchart showing the details of a charging process shown in the Fig. 9 flowchart; Fig. 11 is a block circuit diagam showing another example of the construction of a battery circuit section, in this case built into a computer; Fig. 12 is a flowchart showing a processing operation of the Fig. 11 battery circuit section; Fig. 13 is a flowchart showing the details of a charging process shown in the Fig. 12 flowchart; Fig. 14 is an explanatory diagram showing an embodiment of a second aspect of the invention in which a single auxiliary battery unit is connected to a computer; Fig. 15 is a block diagram showing one example of the construction of the Fig. 14 embodiment; Fig. 16 is a circuit block diagram showing an embodiment of a battery circuit section of a spare battery unit; Fig. 17 is a flowchart showing a processing operation of the Fig. 16 battery circuit section; and Fig. 18 is a flowchart showing the details of a charging process shown in the Fig. 17 flowchart. Fig. 1 shows the first embodiment of the invention in which a plurality of battery units are used. In Fig. 1, a personal computer 10 comprises: a computer main body 12 having a key board; and a closable display section 14 provided as a cover for the computer main body 12. A liquid crystal display panel or the like is provided on the inside of the display section 14 (in the open state as shown in the diagram). For example, two auxiliary battery units (first and second battery units) 16-1 and 16-2 are attached behind the computer main body 12. Fig. 2 shows the manner in which the battery units 16-1 and 16-2 are connected to the computer main body 12 in Fig. 1. First, a connector 24-1 at a tip of a cable 32-1 provided for the auxiliary battery unit (first battery unit) 16-1 is connected to the external power source input terminal of the computer main body 12. The tips of screws 20-1 and 20-2 whose heads are projected to the back of the auxiliary battery unit 16-1 are positioned adjacent to screw holes 18-1 and 18-2 and are screwed and fixed. Subsequently, the auxiliary battery unit (second battery unit) 16-2 is attached. First, a connector 24-2 to which a cable 32-2 on the attaching surface side of the auxiliary battery unit 16-2 is connected is connected to the power source input terminal behind the auxiliary battery unit 16-1 which has already been attached. The screw portions at the tips of screws 22-1 and 22-2 of the battery unit 16-2 are positioned adjacent to the screws 20-1 and 20-2 of the auxiliary battery unit 16-1 which has already been attached. Screw holes are formed in the heads of the screws 20-1 and 20-2. Therefore, by screwing the screw portions at the tips of the screws 22-1 and 22-2 into the screw holes of the head portions of the screws 20-1 and 20-2, the auxiliary battery unit 16-2 can be fixed to the auxiliary battery unit 16-1. A connector 26 of a cable 34 led out from the AC adapter which is used for charging is connected to the power source input terminal of the auxiliary battery unit 16-2 attached at the second time. By connecting the connector 26 from the AC adapter, the auxiliary battery units 16-1 and 16-2 and, further, a battery of the power source circuit section built in the personal computer 10 can be charged. LED display sections 30-1 and 30-2 in which a plurality of light emitting diodes (LED) are arranged are provided in the upper portions of the auxiliary battery units 16-1 and 16-2. The LED display sections 30-1 and 30-2 execute the displaying operations for a period of time during which LED switches 28-1 and 28-2 provided at the sides of LED display sections 30-1 and 30-2 are depressed. Fig. 3, 4, 5, and 6 show a rear view, a plan view, a front view, and a left side view respectively of the auxiliary battery unit 16-1 shown in Fig. 1. As will be apparent from the rear view of Fig. 3, a power source input terminal 36 is provided on the rear side of the auxiliary battery unit 16-1, and the screws 20-1 and 20-2 having screw holes in the heads are provided at two positions of the upper corners of the upper portion. As will be apparent from the plan view of Fig. 4, the LED display section 30-1 using five LEDs is provided in the upper portion of the auxiliary battery unit 16-1. The LED switch 28-1 is provided near the LED display section 30-1. A printed circuit board 40 on which a circuit unit has been installed and a battery pack 38 are provided in the auxiliary battery unit 16-1 as shown by a broken line. In the embodiment, eight NiCd cells are assembled in the battery pack 38 in a state in which they are connected in series. Since each NiCd cell has a nominal voltage of 1.2 V, the nominal output voltage of the battery pack 38 is equal to 9.6 V. As shown in the front view of Fig. 5, the connector 24-1 connected to the cable 32-1 is enclosed in the concave portion at the left lower corner of the auxiliary battery unit 16-1. Further, as shown in the left side view of Fig. 6, the screw 20-1 passes through the interior of the battery unit 16-1 and the screw portion is projected to the tip. Four cells are enclosed in the battery pack 38 when it is seen from the side, and as shown in Fig. 4, since those cells are provided in two lines, it is known that total eight cells are enclosed. Fig. 7 shows one example of the construction of a power source system embodying the invention which makes use of two auxiliary battery units (first embodiment). The personal computer 10 has a computer circuit 44 therein. A power source is supplied to the computer circuit 44 from a power source circuit section (further battery unit contained within the computer housing) 46. A main battery pack is enclosed in the power source circuit section 46. A current consumption of the computer circuit 44 is, for example, equal to or larger than 160 mA in the operating mode, and is equal to or less than 1 mA in the stand-by mode. An input connector 48 is provided for the power source circuit section 46. The auxiliary battery unit (first battery unit) 16-1 has an input connector 50-1, a battery circuit section 52-1, and an output connector 54-1. Similarly, the battery unit (second battery unit) 16-2 also has an input connector 50-2, a battery circuit section 52-2, and an output connector 54-2. An AC adapter 42 receives, for example, a commercially available voltage of AC 100 V and outputs a specified DC voltage. In the embodiment, the AC adapter 42 generates DC 15 V and has a current capacity equal to 1.33 A. The AC adapter 42 is connected whilst the personal computer 10 and the auxiliary battery units 16-1 and 16-2 are charged. It is also possible to use the personal computer 10 by connecting the AC adapter 42 when it is used at a location where the AC power source is obtained. However, since the personal computer 10 is fundamentally used as a portable type, it will be appreciated that the AC adapter 42 is not normally connected to the computer 10 during use thereof, Fig. 8 shows one example of the circuit construction of the auxiliary battery unit which is used in the first embodiment. A noise filter 100 is provided to the output side of an input connector 50. A power source line from the noise filter 100 passes through a Zener diode 102, and a fuse 104 is connected to an analog switch 106 which operates as a first discharge switch. An output of the analog switch 106 is connected via a sense resister 108 (used to detect output current) to an output connector 52 through a noise filter 110. For example, a resistor of 1 Ω is used as a sense resister 108. A battery pack 112 is formed by serially connecting eight NiCd cells 114. Since an output voltage at full charge of one NiCd cell 114 is nominally equal to 1.2 V, the battery pack 112 nominally generates 9.6 V in a state of full charge . A capacity of the battery pack 112 is equal to 1400 mA/h, for example. The battery pack 112 has therein a thermistor 164 to detect an internal temperature. A charging system for the battery pack 112 is as follows. An output line of the noise filter 100 connected to the input connector 50 is branched and connected to a high speed charging circuit 122. An output of the high speed charging circuit 122 passes through a Zener diode 124 and is connected to a plus side of the battery pack 112. In parallel with the high speed charging circuit 122, a serial circuit, or trickle resistor 126, and an analog switch 128 is connected. A resistor of 470 Ω is used as the trickle resistor 126. A discharging system from the battery pack 112 will now be described. The plus side of the battery pack 112 is connected to an analog switch 118 through a sense resistor 116 used to detect a discharge current. The analog switch 118 operates as a second discharge switch. A resistor of 1 Ω is used as a sense resistor 116. An output of the analog switch 118 is connected to a cathode side of the Zener diode 102 through a Zener diode 120. Due to this, both of the analog switches 118 and 106 must be turned on in order to discharge the battery pack 112. A charge control and a discharge control for the battery pack 112 are executed by a microprocessor 130. Regulators 134 and 142 are provided as a power source section to produce a power source voltage of the whole circuit including the microprocessor 130. A voltage on the equipment side of the fuse 104 is applied to the regulator 134 through a switching circuit 132 and a fuse 105. The switching circuit 132 is turned on when an input voltage exceeds, for example, 4 V, and supplies a power source voltage to the regulator 134. The regulator 134 converts the input voltage into a predetermined output constant voltage Vccl. For instance, 3.2 V is used as a power source voltage Vccl. A reference voltage generating circuit 136 generates a reference voltage Vcc2, for example, 1.235 V on the basis of the output voltage Vcc1 provided by the regulator 134. The reference voltage is used by the AD convertor to supply data to the microprocessor 130. The regulator 142 receives the input voltage when an analog switch 140 is turned on and generates a power source voltage Vcc3, for example, 3. 0 V which is supplied to the microprocessor 130. The analog switch 140 is turned on in response to a control signal E9 when the microprocessor 130 detects that an AC adaptor is connected to the input connector 50. Therefore, in the case where the AC adapter is not connected to the input connector 50, the analog switch 140 is turned off and the power source voltage Vcc3 from the regulator 142 is cut off. The power source voltage Vcc3 from the regulator 142 is mainly used as a power source voltage of a charging circuit system. Due to this, during discharge control when no AC adapter is connected, the regulator 142 is cut off, thereby preventing electric power consumption due to the charging circuit system. A resetting circuit 138 operates when the power source voltage Vccl from the regulator 134 is obtained and generates a power-on reset signal El to the microprocessor 130. In response to the power-on reset signal E1, the microprocessor 130 executes an initial reset. The microprocessor 130 has a charge control section 182, a discharge control section 184, and a display control section 186 which are realized by a program control. When the charge control section 182 detects the connection of the AC adapter, the charge control section 182 makes the high speed charging circuit 122 operative on the basis of a detection signal E3 (output current measure) produced by an output current detecting circuit 150 in this instance, thereby allowing the charging operation of the battery pack 112 to be executed. Explaining in detail, a check is first made to see if the AC adapter is connected to the input connector 50 or not on the basis of a voltage detection signal E2 obtained from a voltage divider arrangement comprising resistors 146 and 148 which form a voltage detecting circuit 144. An input voltage from the input connector 50 is equal to DC 15 V in the case where the AC adapter is connected, DC 9.6 V in the case where another auxiliary battery unit is connected, and DC 0V in the case in which neither the AC adapter nor any other auxiliary battery unit is connected. Therefore, the charge control section 182 of the microprocessor 130 can recognize the connection of the AC adapter by a voltage detection of DC 15 V on the basis of the voltage detection signal E2 from the voltage detecting circuit 144. When the connection of the AC adapter is detected, the charge control operation by the charge control section 182 is started. The charge control operation is executed according to the magnitude of the current detection signal E3 from the output current detecting circuit 150. For example, Ith = 1 mA is first set as a threshold current Ith of the output current. The charge control section 182 makes the high speed charging circuit 122 operative when the detected output current is equal to or less than the threshold current Ith = 1 mA, thereby causing the battery pack 112 to be charged and causing maximum value of the charging current to be set to 1.2 A. The charging time of the battery pack 112 by high speed charging is, for example, 1.2 hours. When the output current detected by the output current detecting circuit 150 is equal to or larger than the threshold current Ith = 1 mA, the charge control section 182 stops the operation of the high speed charging circuit 122 and turns on the analog switch 128 and switches to the trickle charging by the trickle resistor 126. The trickle charging is executed while the personal computer is operating. The high speed charging circuit 122 and the analog switch 128 for trickle charging are controlled by control signals E12 and E13 from the microprocessor 130. When the charge control section 182 detects the connection of the AC adapter, the control signal E12 is made active. The high speed charging circuit 122 operates by negative logic on the basis of the control signals E12 and E13. Therefore, upon the detection of the AC adapter, the control signal E12 is set to the low level. The control signal E13 becomes active when the output current is equal to or less than the threshold current Ith = 1 mA. That is, since it is a negative logic signal, the control signal E13 is set to the low level. The high speed charging circuit 122 operates when both of the control signals E12 and E13 are set to the low level, thereby executing the charging at a high speed. The high speed charging circuit 122 has an NAND gate to which the control signals E12 and E13 are supplied, a transistor switch which is turned on/off by an output of the NAND gate, and a current limiting circuit to limit the charge current to a predetermined high speed charging current value in the ON state of the transistor switch. The analog switch 128 operates by positive logic. When the output current detected by the output current detecting circuit 150 exceeds the threshold current Ith = 1 mA, the control signal E13 changes from the low level to the high level. Due to this, the operation of the high speed charging circuit 122 is stopped, the analog switch 128 is turned on at the same time, and the trickle charging of the battery pack 112 via the trickle resistor 126 is started. During trickle charging the charge current is determined by a resistance value of 470 Ω of the trickle resistor 126 according to the voltage difference between the input voltage from the AC adapter and the present charging voltage of the battery pack 112. The charging operation of the charge control section 182 is stopped in any one of the following cases: namely, when a predetermined time, measured by a timer activated at the start of the charging, for example, 1.2 hours of the high speed charging elapses; when an abnormal temperature is detected by the thermistor 164 provided for the battery pack 112; and further, when the full charging is detected on the basis of a change in charging voltage of the battery pack 112. In order for the microprocessor 130 to recognize such a state of the battery pack, an AD converter 156 to detect a battery current, an AD converter 158 to detect a temperature, an AD converter 160 to detect a battery voltage, and an AD converter 162 to detect the presence or absence of the battery are provided. The AD converter 156 to detect the battery current receives a voltage across the sense resistor 116 provided for the discharge circuit and converts the received voltage into a digital voltage detection signal E4 which is supplied to the microprocessor 130. The AD converter 158 to detect the temperature supplies a temperature detection signal E5,based on the thermistor 164 built into the battery pack 112,to the microprocessor 130. The AD converter 160 to detect the battery voltage supplies a voltage detection signal E6, obtained converting the charging voltage of the battery pack 112, to the microprocessor 130. Further, the AD converter 162 to detect the presence or absence of the battery supplies a detection signal E7 indicative of the presence or absence of the connection of the battery pack 112 to the microprocessor 130. Further, a signal line which is pulled up by a resistor 166 to the power source voltage +Vcc1 passes into the battery pack 112 as shown by a broken line, and provides the microprocessor 130 with a detection signal E8 in the event of a leakage of the battery pack 112. For example, when moisture or water enters the battery pack 112, a shorting current flows through the resistor 166 and the leak detection signal E8 drops to 0 V. Therefore, the microprocessor 130 can detect a short-circuit of the battery pack 112 by such a voltage drop. The display control section 186 provided in the microprocessor 130 executes a display control of the LED display section 30. Five LEDs 170, 172, 174, 176, and 178 are provided in the LED display section 30 and are driven by control signals E15, E16, E17, E18, and E19. The display control section 186 operates and drives the display section 30 when an LED switch 28 is in the ON position. The LED switch 28 is pulled up to the power source Vcc1 through a resistor 168. When the LED switch 28 is in the OFF position, a switch signal E14 is at the high level because it is pulled up to the power source voltage Vcc1. When the LED switch 28 is turned on, the switch signal E14 is set to the low level, so that the display control section 186 operates. The LED 170 is lit up by the control signal E15 when the input of DC 15 V by the AC adapter is detected. The LEDs 172, 174, and 176 are sequentially lit up by the control signals E16 to E18 in accordance with the magnitude of the charging voltage of the battery pack 112. For example, the three LEDs 172, 174, and 176 are lit up when the battery pack 112 is fully charged, whereas just the two LEDS 174 and 176 are lit up when the voltage is low. Only Only the LED 176 is lit up when the voltage is even lower. Further, the LED 178 flickers in accordance with the control signal E19 when a decrease in the battery voltage is detected. Therefore, when the LED 178 flickers while the LED switch 28 is ON, it will be understood that it is necessary to charge. The microprocessor 130 operates using clocks of 1.8 MHz and 32 KHz from quartz oscillators 152 and 154 provided externally of the microprocessor. For example, a four bit microprocessor is used as a microprocessor 130. The flowchart of Fig. 9 shows a processing operation by the microprocessor 130 provided in Fig. 8. When a power source voltage exceeding 4 V is supplied, the switching circuit 132 is turned on and supplies the power source voltage to the regulator 134. In response to the power-on reset signal E1 from the resetting circuit 138, the microprocessor 130 executes an initialization in step S1. Subsequently, a check is made to see if the battery pack 112 is connected or not in step S2. If the battery pack 112 is not connected, an alarm is generated in step S8 and the processing routine is finished as an abnormal state. When the battery pack 112 is normally connected, step S3 follows and a check is made if an AC adapter has been connected or not. Specifically speaking, it is judged that the AC adapter is connected when the input voltage is equal to DC 15 V due to the voltage detection signal E2 from the voltage detecting circuit 144. When the AC adapter is connected, step S9 follows. The analog switch 106, serving as a first discharge switch, is turned on and the analog switch 118, serving as a second discharge switch, is turned off. The processing routine advances to a charging process in step S10. The details of the charging process in step S10 are shown as a subroutine in Fig. 10. In the case where it is judged that no AC adapter is connected in step S3, step S4 follows and a check is made to see if another auxiliary battery unit has been connected or not. When another auxiliary battery unit is connected, the input detection voltage by the voltage detecting circuit 144 is equal to DC 9.6 V. When the connection of another auxiliary battery unit is judged, in step S11 the analog switch 106 serving as the first discharging switch is turned on in a manner similar to the case in step S9, the analog switch 118 serving as the second discharging switch is turned off, and the supplied voltage from the connected auxiliary battery unit, received via the input connector 50, is supplied directly to the output connector 52 by the analog switch 106 which is in the ON state. When another battery unit is not connected in step S4, namely when the input detection voltage is equal to 0 V, step S5 follows. The analog switches 118 and 106 (first and second discharging switches respectively) are each turned on. Due to this, a discharging circuit from the battery pack 112 to the output connector 52 is formed and a discharging state using the unit's own battery pack 112 is obtained. When the discharging state is established in step S5, a drop in the battery voltage is discriminated in step S6 and an overcurrent is detected in step S7. When such drop in the battery voltage or such an overcurrent is detected, step S12 follows and the analog switch 118 (second discharging switch) is turned off and the discharging operation of the battery pack 112 is stopped. As for stopping the discharging due to the drop in the battery voltage in step S6, in addition to the process of the microprocessor 130, when the input voltage of the switching circuit 132 provided in the power source circuit section is equal to or less than 4 V, the power supply to the regulator 134 is cut off. Due to this, the operation of the whole circuit section including the microprocessor 130 is stopped, the discharging of the battery pack 112 is substantially stopped, thereby preventing a damage of the battery pack 112 by the excessive discharge. Fig. 10 shows details of the charging process shown in step S10 in Fig. 9 as a subroutine. When the microprocessor 130 detects the connection of the AC adapter, the charging process in Fig. 10 is started. In step S1, a check is first made to see if the output current detected by the output current detecting circuit 150 is equal to or less than the threshold current Ith or not. For example, when Ith = 1 mA and the output current is equal to or less than 1 mA, step S2 follows and the high speed charging circuit 122 is operated and the high speed charging process is started. During the high speed charging, in step S3 a check is made to see if the charging has been completed or not by discriminating whether the timer activated by the start of the charging has reached a set time, for example, 1.2 hours or not. In step S4, a completion of the charging is judged on the basis of the battery voltage. If the battery pack 112 uses NiCd cells 114, the charging voltage increases during charging with the elapse of time and it starts to drop when it is fully charged. Therefore, in step S4, it is judged that the charging has been completed when the value of a negative time change ratio due to a decrease in charging voltage exceeds a predetermined threshold value. Further in step S5, a check is made to see if the detection temperature measured by the thermistor 164 provided in the battery pack 112 is equal to or higher than a specified value or not. Since there is a fear that, when the charging of the battery pack 112 is suddenly executed the internal temperature rises and the NiCd cell itself is damaged, the charging is stopped when the detection temperature is equal to or higher than the specified value. When one of the results of the judgment in steps S3, S4, and S5 is obtained, step S6 follows and a charge stopping process to stop the operation of the high speed charging circuit 122 is executed. Such a high speed charging process is executed in a stand-by mode in which the personal computer 10 is not used. On the other hand, when the personal computer 10 is used, the output current exceeds the threshold value Ith. In this case, the processing routine advances from step S1 to step S7 and a trickle charging process is executed. That is, the operation of the high speed charging unit 122 is stopped and at the same time, the analog switch 128 is turned on. During trickle charging the charging current depends on the resistance value (470 Ω) of the trickle resistor 126 and a voltage difference between the supply voltage of the AC adapter at that time and the charging voltage of the battery pack 112. With respect to the trickle charge, a check is also made to see if there is any abnormality due to the completion of the charging by the battery voltage in step S4 or the increase in battery temperature in step S5. When one of the above conditions is judged, a charge stopping process is executed in step S6. Fig. 11 shows the power source circuit section 46 provided in the personal computer 10 shown in Fig. 7. The power source circuit section 46 which is provided in the personal computer is a circuit from which the analog switch 106 as a first discharge switch provided in the battery circuit section of the auxiliary battery unit shown in Fig. 8 is eliminated but otherwise the remaining circuit construction is substantially the same. Therefore, in Fig. 11, the same component elements as those shown in Fig. 8 are designated by substantially the same reference numerals with respect to the "unit" digit and the "tens" digit but the "hundreds" digit is changed from "1" to "2". For example, the noise filter 100 provided subsequently to the input connector 50 in Fig. 8 is shown as a noise filter 200 in Fig. 11. Fig. 12 is a flowchart showing the processing operation of the power source circuit section provided in the personal computer in Fig. 11. The flowchart of Fig. 12 corresponds to the flowchart of Fig. 9 relating to the auxiliary battery unit. The processes in steps 9 to 11 in Fig. 9 are eliminated and the ON operations of the first and second discharge switches in step S5 is changed to the ON operation of a single discharge switch. That is, the power source circuit section in Fig. 11 provided in the personal computer executes the discharge control using only an analog switch 218 provided in the discharging line of the battery pack 212. Due to this, in the case where the input voltage from the input connector 48 is set to DC 15 V (indicating that an AC adapter is connected) or in the case where the input voltage is set to DC 9.6 V (which is necognised as a supplied voltage from an auxiliary battery unit), the analog switch 218 is turned off and the discharging of the computer's own battery pack 212 is stopped. When the input voltage from the input connector 48 is equal to 0V, the analog switch 218 is turned on, thereby enabling discharging from the computer's own battery pack 212. Fig. 13 shows the charging process by the power source circuit section provided in the personal computer shown in step S9 in Fig. 12 as a subroutine. The charging process is substantially the same process as that in the case of the auxiliary battery unit shown in Fig. 10. The charging operation and discharging operation of the system as a whole when the two auxiliary battery units 16-1 and 16-2 are connected in such a series configuration to the personal computer 10 as shown in Fig. 7 will now be described. The charging operation is executed by connecting the AC adapter 42 to the last auxiliary battery unit 16-2. The AC adapter 42 generates DC 15 V, the battery circuit sections 52-2 and 52-1 of the auxiliary battery units 16-1 and 16-2 detect the connection of the AC adapter 42 from their respective input voltages of DC 15 V, and the respective charging control sections of the units 16-1 and 16-2 are set into the operating mode. Similarly, the power source circuit section 46 of the personal computer 10 also recognizes the connection of the AC adapter 42 from its input voltage of DC 15 V and sets its charging control section into the operating mode. If it is now assumed that the computer circuit 44 is in a stand-by mode, the high speed charging is executed first to the battery pack 212 of the power source circuit section 46 provided in the personal computer 10 by the charging control of each of the power source circuit section 46 and the battery circuit sections 52-1 and 52-2. The current due to the high speed charging is detected by the auxiliary battery units 16-1 and 16-2, and since the current exceeds the threshold current Ith, the trickle charging state is obtained. That is, the high speed charging is started from the power source circuit section 46 of the personal computer 10. When the high speed charging of the computer's own battery pack by the power source circuit section 46 of the personal computer 10 is completed, the output current flowing in the auxiliary battery units 16-1 and 16-2 becomes the stand-by current of the personal computer 10 again. Each of those units starts the charging operation again. However, the output current flowing upon commencement of charging in the auxiliary battery unit 16-1 located nearest to the personal computer 10 is detected by the other auxiliary battery unit 16-2 and the charging mode thereof is switched to trickle charging. Due to this, when the high speed charging of the personal computer 10 is completed, the high speed charging of the auxiliary battery unit 16-1 is started subsequently. When the high speed charging of the auxiliary battery unit 16-1 is finished, the charging mode is finally switched to the high speed charging of the auxiliary battery unit 16-2. When the personal computer 10 enters the operating mode and the output current increases during the high speed charging in any one of the personal computer 10 and the auxiliary battery units 16-1 and 16-2, the charging mode is switched from the high speed charging to the trickle charging at that time point. Therefore, each of the charging operations can be sequentially executed while using the personal computer 10. The discharge control in a state in which the AC adapter 42 is detached will now be described. In a state in which the AC adapter 42 is detached, the input voltage of the input connector 50-2 of the auxiliary battery unit 16-2 furthest from the computer is equal to 0V. Due to this, the battery circuit section 52-2 allows its unit's own battery pack to be discharged. In the auxiliary battery unit 16-1 nearest to the personal computer, since the input voltage of the input connector 50-1 is equal to DC 9.6 V due to the connection of the auxiliary battery unit 16-2, the battery circuit section 52-1 detaches its unit's own battery pack and the battery voltage of 9.6 V from the auxiliary battery unit 16-2 is supplied directly to the personal computer 10. In the power source circuit section 46 provided in the personal computer 10, since the input voltage of the input connector 48 is equal to DC 9.6 V, the power source circuit section 46 detaches the computer's own battery pack 212 and supplies 9.6 V, received from outside, directly to the computer circuit 44 as a power source voltage. When the discharging of the auxiliary battery unit 16-2 is finished, specifically speaking, when the battery voltage in that unit drops to 4 V or less, the input voltage to the input connector 50-1 of the auxiliary battery unit 16-1 becomes 0 V due to the detachment of the battery pack. Therefore, the battery circuit section 52-1 commences discharging and connects its unit's own battery pack, thereby supplying DC 9.6 V to the personal computer 10. The power source circuit section 46 of the personal computer 10 is still in a state in which the discharging of the computer's own battery pack is prevented. When the discharging of the auxiliary battery unit 16-1 is finished, specifically speaking, when the discharging voltage is lower than 4 V, the input voltage of the input connector 48 of the personal computer 10 is equal to 0 V due to the detachment of the battery unit. Therefore, the discharging operation of the power source circuit section 46 is executed, the computer's own battery pack is connected to the discharging line and the discharging to supply a power source to the computer circuit 44 is started. As mentioned above, the discharging operation is executed sequentially, starting from the auxiliary battery unit 16-2 connected furthest in the series from the personal computer 10. The maximum value (n) of the auxiliary battery units which can be connected to the personal computer 10 is set to the maximum value (n) which satisfies the following equation since when the power source is lower than the necessary power source voltage, the personal computer 10 is stopped. V AC - V F x n > V dd Where, V AC denotes an output voltage of the AC adapter, V F denotes a drop voltage by the auxiliary battery unit, and V dd indicates an input power source voltage which is necessary for the personal computer 10. For instance, when it is now assumed that V AC = 15 V, V F = 1V, and V dd = 9V, n < 6 is obtained. Thus, in this instance a maximum of six auxiliary battery units can be connected. Fig. 14 shows a second embodiment of the invention. In the embodiment of Fig. 14, only one auxiliary battery unit (the second battery unit) 16 is provided externally for the personal computer 10. The auxiliary battery unit 16 has the same structure as that of one of the auxiliary battery units shown in Fig. 1. Fig. 15 shows a system construction in the modified invention of Fig. 14. The personal computer 10 has the computer circuit 44, power source circuit section (first battery unit) 46, and input connector 48 in a manner similar to Fig. 7 The auxiliary battery unit 16 has the input connector 50, battery circuit section 52, and output connector 54. When charging, the AC adapter 42 is connected to the input connector 50 of the auxiliary battery unit 16. The battery circuit section 52 of the auxiliary battery unit 16 has a circuit construction shown in Fig. 16. In the single auxiliary battery unit (second battery unit) shown in Fig. 16, the analog switch 118, which was provided in the discharging line of the battery pack 112 in the auxiliary battery unit in the case where a plurality of auxiliary battery units are connected, is eliminated. The discharging control is executed only by the analog switch 106 provided between the input and output connectors 50 and 52. Since the other circuit construction is similar to that in the embodiment of Fig. 8, the same component elements are designated by the same reference numerals. A charge control section 382, a discharge control section 384, and a display control section 386 which are realized by a program control are provided for the microprocessor 130. When the circuit of the sole auxiliary battery unit provided for the personal computer 10 in Fig. 16 is compared with the power source circuit section provided in the personal computer 10 shown in Fig. 11, each circuit has only the single analog switch 106 or the single analog switch 218, as the case may be, as a discharging switch, and the processes of the charge control sections 282 and 382 are almost the same although the positions of the analog switches 106 and 218 are different in the two circuits. Fig. 17 shows the processing operation in the auxiliary battery unit in Fig. 16. The processing operation itself is substantially the same as that of Fig. 12 except that the discharging switch in each of steps S5 and S10 is the analog switch 106 in the case of Fig. 16 rather than the analog switch 218 as in the case of Fig. 11. With respect to Fig. 18 in which the charging process in step S9 in Fig. 17 is shown as a subroutine, the process is almost the same as that shown in Fig. 13. In the operation of the system shown in Fig. 15, as a whole, the battery pack of the power source circuit section (first battery unit) 46 of the personal computer 10 is first charged and the battery pack of the battery circuit section 52 of the auxiliary battery unit (second battery unit) 16 is subsequently charged. On the other hand, the discharging operation is started from the battery pack of the auxiliary battery unit (second battery unit) 16 and when discharging of the auxiliary battery unit 16 is finished, the discharging mode is switched to the discharging from the battery unit of the power source circuit section (first battery unit) 46. That is, with respect to the charging and discharging as well, the charging and discharging operations are executed essentially in the same order as the first embodiment having a plurality of auxiliary battery units which can be connected externally as mentioned above. Although the above embodiment has been described with respect to the case where the NiCd cells are used in the battery pack as an example, it is also possible to use other chargeable battery cells. As a way of judging full charging based on the charging voltage in the charge control, a phenomenon which is peculiar to the NiCd cell is exploited, namely that the charging voltage which has risen is decreased by the completion of the charging is captured and judged. With respect to other kinds of battery cells, it is sufficient to judge the full charging from a change in charging voltage according to charging characteristics which are peculiar to such cells. Further, the invention is not limited by the numerical values shown in the above embodiments. As described above, an embodiment of the present invention can provide a power source system of a portable information processing system using a battery which enables operation over long periods of time by connecting and fixing an auxiliary battery unit to the system main body.

Claims: Apparatus comprising a portable electrical device (10) and respective first and second battery units (16-1, 16-2; 16, 46), each battery unit including one or more rechargeable batteries (114; 114, 214), for supplying electrical power to circuitry (44) of the device; each of the battery units having an input (50-1, 50-2; 50, 48) for receiving electrical power for charging its said one or more batteries and an output (54-1, 54-2; 54, -) for delivering electrical power from its said one or more batteries; and the battery units being connected and controlled, when the apparatus is in use, such that when an external power supply source (42) is connected to the apparatus the first battery unit (16-1; 46) is charged first and then the second battery unit (16-2; 16) is charged, and such that when no such external power supply source is connected the said circuitry (44) is powered first by the said second battery unit, until that unit is discharged, and then by the said first battery unit; characterised in that, during such sequential charging and such sequential powering, the first and second battery units are connected together in a series configuration in which the input of the first battery unit (16-1; 46) is connected to the output of the second battery unit (16-2; 16), the said circuitry (44) being connected on the output side of the first battery unit ; and in that each of the battery units has control means (130; 130, 230) which co-operate to bring about the said sequential charging when such an external power supply source is connected to the apparatus, and to bring about the said sequential powering when no such external power supply source is connected. Apparatus as claimed in claim 1, wherein the said first and second battery units (16-1, 16-2) are contained in respective housings external to the housing of the said device (10). Apparatus as claimed in claim 2, wherein: the said portable electrical device (10) is an information processing device having a power source input terminal (48); and when the first and second battery units (16-1; 16-2) are connected together in the said series configuration those units are connectible physically to the said device housing and the said first battery unit (16-1) is connected electrically to the said power source input terminal (48). Apparatus as claimed in claim 3, wherein in each said battery unit (16-1; 16-2) the said one or more rechargeable batteries is/are made up of a plurality of battery cells (114) connected in series and enclosed in a battery pack (112); and each said battery unit (16-1; 16-2) further includes: an input terminal (50) connectible to an output terminal (52) of another battery unit or an output terminal (26) of such an external power supply source (42) ; an output terminal (54) connectible to an input terminal (50) of another such battery unit or said power source input terminal (48) of said information processing device (50); voltage detecting means (144) for detecting an input power source voltage applied to the said input terminal (52); current detecting means (150) for detecting an output current flowing through the said output terminal (52); first discharge switching means (106) for turning on/off the supply of power to said output terminal (54) ; second discharge switching means (118) for turning on/off the supply of power from the unit's said battery pack (112); charge switching means (122) for turning on/off the supply of power from said input terminal (50) to the unit's said battery pack (112); charge control means (182) operable to detect the connection of such a external power supply source (42), based on the detection by said voltage detecting means (144) of such an input power source voltage, and, upon detecting such connection, to cause said charge switching means (122) to turn on the said supply of power from said input terminal (50) to the unit's said battery pack (112), so as to bring about charging of that battery pack, provided that the output current detected by said current detecting means (150) is equal to or less than a predetermined value; and discharge control means (184) operable, when the connection of such an external power supply source (42) or of another such battery unit is detected based on the detection by said voltage detecting means (144) of such an input power source voltage, to cause said first discharge switching means (106) to turn on the said supply of power to the said output terminal (52) and also to cause the said second discharge switching means (118) to turn off the said supply of power from the unit's said battery pack (112), so as to pass externally-supplied power from the said input terminal (50) to the said output terminal (52), and also operable, when it is detected that no such external power supply source and no such other battery unit is connected based on the non-detection by said voltage detection means (144) of such an input power source voltage, to cause the first and second discharge switching means (106,118) to turn on respectively the said supply of power to the said output terminal (52) and the said supply of power from the unit's said battery pack (112) so as pass to the said output terminal (52) internally-supplied power from that battery pack. Apparatus according to claim 4, wherein said discharge control means (184) causes the second discharge switching means (118) to turn off the said supply of power from the unit's said battery pack (112) if it is detected that the discharge current from that battery pack is greater than or equal to a predetermined overcurrent value. Apparatus according to claim 4 or 5, wherein said discharge control means causes the first and second discharge switching means (106,118) to turn off respectively the said supply of power to the said output terminal (52) and the said supply of power from the unit's said battery pack (112) if it is detected that the discharge voltage of that battery pack is equal to or less than a specified voltage. Apparatus as claimed in any one of claims 3 to 6, wherein the said device (10) also has a further such battery unit (46), contained within the device housing, the input (48) of which further battery unit is connected to the output (54-1) of the said first battery unit (16-1) when the apparatus is in use and the output of which further battery unit is connected to the said circuitry (44), the said further battery unit (46) having control means (230) which co-operate with the control means (130) of the said first and second battery units (16-1, 16-2), when such an external power supply source (42) is connected on the input side of the said second external power supply source (16-2), to cause the said further battery unit (46) to be charged before the said first battery unit (16-1) is charged during the said sequential charging, and which also co-operate, when no such external power supply source is connected, to cause the said circuitry (44) to be powered by the said further battery unit after the said first battery unit has become discharged during the said sequential powering. Apparatus as claimed in claim 1, wherein the said first battery unit (46) is contained within the housing of the said device (10), and the said second battery unit (16) is contained in its own housing which can be connected physically to the device housing when the apparatus is in use. Apparatus as claimed in claim 8, wherein: the said portable electrical device (10) is an information processing device having a power source input terminal (48); and when the first and second battery units (46,16) are connected together in the said series configuration the said second battery unit (16) is connected electrically to the said power source input terminal (48). Apparatus according to claim 9, wherein in the said second battery unit (16) the said one or more rechargeable batteries is/are made up of a plurality of battery cells (114) connected in series and enclosed in a battery pack (112); and the said second battery unit (16) further includes: an input terminal (50) to which an output terminal (26) of such an external power supply source (42) is connectible; an output terminal (52) which is connectible to said power source input terminal (48) of said portable electrical device (10); voltage detecting means (144) for detecting an input power source voltage applied to said input terminal (50); current detecting means (150) for detecting an output current flowing through said output terminal (52); discharge switching means (106) for turning on/off the supply of power to said output terminal (52) ; charge switching means (122) for turning on/off the supply of power from said input terminal (50) to the unit's said battery pack (112); charge control means (382) operable to detect the connection of such a external power supply source, (42) based on the detection by said voltage detecting means (144) of such an input power source voltage, and, upon the detection of such connection, to cause said charge switching means (122) to turn on the said supply of power from the said input terminal (50) to the unit's said battery pack (112), so as to bring about charging of that battery pack, provided that the output current as detected by said current detecting means (150) is equal to or less than a predetermined value; and discharge control means (384) operable, when the connection of such an external power supply source is detected based on the detection by said voltage detecting means (144) of such an input power source voltage, to cause said discharge switching means (106) to turn on the said supply of power to said output terminal (52) so as to pass externally-supplied power to the said portable electrical device, and also operable, when it is detected that no such external power supply source (42) is connected based on the non-detection by said voltage detecting means (144) of such an input power source voltage, to cause the discharge switching means (106) to turn on the said supply of power to said output terminal (52), so as to pass to the said portable electrical device (10) internally-supplied power from the unit's said battery pack. Apparatus according to claim 10, wherein said discharge control means (384) causes said discharge switching means (106) to turn off the said supply of power to said output terminal (52), when internally-supplied power is being passed, if it is detected that the discharge current of the unit's battery pack (112) is greater than or equal to a predetermined overcurrent value. Apparatus according to claim 10 or 11, wherein said discharge control means (384) causes said discharge switching means (106) to turn off the said supply of power to said output terminal (52) if it is detected that the discharge voltage of the unit's said battery pack is less than or equal to a specified voltage. Apparatus according to any one of claims 4 to 6 or 10 to 12, wherein said charge switching means (122) comprises: high speed charging means (122) operable to supply a current near a maximum allowable charge current of the unit's said battery pack (112) so as to bring about charging at a high speed; and trickle charging means (126) connected in parallel to said high speed charging means (122) and operable to supply a trickle charging current which is determined by a voltage difference between said input power source voltage and the charging voltage of the unit's said battery pack (112) and by a specified resistance value; and wherein said charge control means (182; 382) makes said high speed charging means (122) operative when the output current detected by said current detecting means (150) is equal to or less than a predetermined value in a state in which the connection of such an external power supply source is detected, thereby bringing about such high-speed charging, and also makes said trickle charging means (126) operative when the detected output current exceeds that predetermined value, thereby bringing about trickle charging. Apparatus according to any one of claims 4 to 6 or 10 to 13, wherein said charge control means (182; 382) are operable to cause said charge switching means (122) to turn off the said supply of power from the input terminal (50) to the unit's said battery pack (112), so as to stop the charging, when a timer which was activated at the start of the charging indicates that a predetermined amount of time has elapsed. Apparatus according to any one of claims 4 to 6 or 10 to 14, wherein said charge control means (182; 382) are operable to cause said charge switching means (122) to turn off the said supply of power from the input terminal (50) to the unit's said battery pack (112), so as to stop the charging, when temperature detecting means (164; 158) provided for that battery pack detect that the battery pack exceeds a predetermined temperature. Apparatus according to any one of claims 4 to 6 or 10 to 15, wherein said charge control means (182; 382) are operable to monitor the power source voltage of the unit's said battery pack (112) and, if a decrease in the monitored voltage is detected after that voltage has risen, in association with the charging, to exceed a peak voltage, the charge control means (182; 382) causes the charge switching means (122) to turn off the said supply of power from the said input terminal (50) to the unit's said battery pack (112), so as to stop the charging. Apparatus according to any one of claims 3 to 16, further comprising display means (30) for indicating a state of the battery unit. Apparatus according to claim 17, wherein said display means (30) indicates at least whether such an input power source voltage is applied to the input terminal, a charging state, and a state of the battery voltage of the unit's said battery pack (112). Apparatus according to claim 17 or 18, wherein said display means (30) has display switching means (28) for switching the display means (30) from an ON state, in which such indications are produced by the display means (30), to an OFF state in which those indications are not produced. Apparatus according to claim 7 or 9 or to any one of claims 10 to 19 when read as appended to claim 7 or 9, wherein: in said battery unit (46) contained in the device housing the said one or more rechargeable batteries is/are made up of a plurality of battery cells (214) connected in series and enclosed in a battery pack (212), and the said power source input terminal (48) is connectible to an output terminal (52) of another such battery unit or to an output terminal (26) of such an external power supply source (42); and the said battery unit (46) contained in the device housing further includes: voltage detecting means (244) for detecting an input voltage applied to said power source input terminal (48); current detecting means (250) for detecting an output current flowing to said circuitry (44); discharge switching means (218) for turning on/off the supply of power from said battery pack (212); charge switching means (222) for turning on/off the supply of power from said power source input terminal (48) to said battery pack (212); charge control means (282) operable to detect the connection of such an external power supply source (42), based on the detection by said voltage detection means (244) of such an input voltage, and, upon the detection of such connection, to cause charge switching means (222) to turn on the said supply of power from the said power source input terminal (48) to the device's said battery pack (212), so as to bring about charging of that battery pack, provided that the output current detected by said current detecting means (250) is equal to or less than a predetermined value; and discharge control means (284) operable, when the connection of such an external power supply source (42) or such a battery unit (16) is detected based on the detection by said voltage detecting means (244) of such an input voltage, to cause said discharge switching means (218) to turn off the said supply of power from the device's said battery pack and also operable, when it is detected that no such external power supply source and no such battery unit is connected based on the non-detection of such an input voltage, to cause the said discharge switching means (218) to turn on the said supply of power from the device's said battery pack, so that the said circuitry (44) is supplied with power from that battery pack. Apparatus according to claim 20, wherein said charge switching means (222) of the said portable electrical device (10) comprises: high speed charging means (222) operable to supply a current near a maximum allowable charge current of the device's said battery pack (212) so as to bring about charging at a high speed; and trickle charging means (226) connected in parallel to said high speed charging means (222) and operable to supply to the device's said battery pack (212) a trickle charging current which is determined by a voltage difference between the input power source voltage and the charging voltage of that battery pack (212) and by a specified resistance value; and wherein said charge control means (282) makes the high speed charging means (222) operative when the output current detected by said current detecting means (250) is equal to or less than a predetermined value in a state which the connection of such an external power supply source (42) is detected, thereby bringing about the said high-speed charging, and also makes said trickle charging means (226) operative when the detected output current exceeds said predetermined value, thereby bringing about trickle charging. Apparatus according to claim 20 or 21, wherein said charge control means (282) are operable to cause said charge switching means (222) to turn off the said supply of power from said power source input terminal (48) to the device's said battery pack (212), so as to stop the charging, when a timer activated at the start of the charging indicates that a predetermined amount of time has elapsed. Apparatus according to claim 20, 21 or 22, wherein said charge control means (282) are operable to cause said charge switching means (222) to turn off the said supply of power from said power source input terminal (48) to the device's said battery pack (212), so as to stop the charging, when it is detected by temperature detecting means (264, 258) provided for that battery pack that the battery pack exceeds a predetermined temperature. Apparatus according to any one of claims 20 to 23, wherein said charge control means (282) are operable to monitor the power source voltage of said battery pack (212) and, if a decrease in the monitored voltage is detected after that voltage has risen, in association with the charging, to exceed a peak voltage, said charge control means (282) cause said discharge switching means (222) to turn off the said supply of power from the said power source input terminal (48) to the device's said battery pack (212), so as to stop the charging. Apparatus according to any one of claims 20 to 24, further comprising display means (280) for indicating a state of said portable electrical device (10). Apparatus according to claim 25, wherein said display means (280) indicates at least whether such an input voltage is applied to said input terminal (48), a charging state, and a state of the battery voltage of the device's said battery pack (212). Apparatus according to claim 25 or 26, wherein said display means (280) has display switching means (282) for switching the display means (280) from an ON state, in which such indications are produced by the display means (280), to an OFF state in which those indications are not produced. Apparatus according to any one of claims 20 to 27, wherein said discharge control means (284) cause said discharge switching means (218) to turn off the said supply of power from the device's said battery pack if it is detected that the discharge current of that battery pack is greater than or equal to a predetermined overcurrent value. Apparatus according to any one of claims 20 to 28, wherein said discharge control means (284) causes said discharge switching means (218) to turn off the said supply of power from the device's said battery pack to said circuitry (44) if it is detected that the discharging voltage of that battery pack is equal to or less than a specified voltage. Apparatus as claimed in any preceding claim, further including such an external power supply source (42), the external power supply source comprising AC adaptor means for converting an AC power source into a DC power source.

Inventors: MATSUDA KOUICHI, OBITSU TOSHIRO, OZAWA HIDEKIYO, YAMAMOTO TETSUO, YANO HIDETOSHI, MATSUDA, KOUICHI, OBITSU, TOSHIRO, OZAWA, HIDEKIYO, YAMAMOTO, TETSUO, YANO, HIDETOSHI, MATSUDA, KOUICHI, C/O FUJITSU LIMITED, OBITSU, TOSHIRO, C/O FUJITSU LIMITED, OZAWA, HIDEKIYO, C/O FUJITSU LIMITED, YAMAMOTO, TETSUO, C/O FUJITSU LIMITED, YANO, HIDETOSHI, C/O FUJITSU LIMITED
Applicants: FUJITSU LTD, FUJITSU LIMITED
Application year: 1994
Main classification: H02J9
IPC codes: G06F1, H02J9, H02J7